1. Issues in Ad Hoc Wireless Networks
Medium access scheme
Routing
Multicasting
Transport layer protocol
Pricing scheme
Quality of service provisioning
Self-organization
Security
Energy management
Addressing and service discovery
Scalability
Deployment considerations

2. Medium Access Scheme Distributed operation Synchronization
The MAC protocol design should be fully distributed involving minimum control overhead
Synchronization
Mandatory for TDMA-based systems. Synchronization involves usage of scarce resources such as bandwidth and battery power
Hidden terminals
Can significantly reduce the throughput of a MAC protocol.
Hence the MAC protocol should be able to alleviate the effects of hidden terminals
Exposed terminals
To improve the efficiency of the MAC protocol, the exposed nodes should be allowed to transmit in a controlled fashion without causing collision to the on-going data transfer
Access delay
The MAC protocol should attempt to minimize the delay
Throughput
The important considerations for throughput enhancement are minimizing the occurrence of collision, maximize channel utilization, and minimize control overhead.

3. Real-time traffic support
Fairness
Equal share or weighted share of the bandwidth to all
competing nodes
Real-time traffic support
Voice, video and real-time data require explicit support from the MAC protocol
Resource reservation
Such as BW, buffer space, and processing power
Capability for power control
Reduces the energy consumption, decrease in interference , increase in frequency reuse
Adaptive rate control
Variation in the data bit rate
Use of directional antennas
Increased spectrum reuse, reduction in interference, and reduced power consumption

4. Routing The Major Challenges of Routing Protocol are
Mobility: results in frequent path break, packet
collision, and difficulty in resource reservation
Bandwidth constraint: BW is shared by every node
Error-prone and share channel: high bit error rate
Location-dependent contention: distributing the
network load uniformly across the network
Other resource constraint: computing power, battery power, and buffer storage

5. The Major Requirement of Routing Protocol
Minimum route acquisition delay
Quick route reconfiguration: to handle path breaks
Loop-free routing
Distributed routing approach
Minimum control overhead
Scalability
Provisioning of QoS
Bandwidth, delay, jitter, packet delivery ratio
Supporting differentiated classes of services
Support for time-sensitive traffic
Hard real-time and Soft real-time traffic
Security and privacy

6. Multicasting The Major Issues in Multicast Routing Protocols
Robustness
recover and reconfigure quickly from link breaks
Efficiency
minimum number of transmissions to deliver a data packet to all the group members
Minimal Control overhead
QoS support
Efficient group management
Scalability
Security

7. Transport Layer Protocols
Objectives: setting up and maintaining
End-to-end connections, reliable end-to-end data
delivery, flow control, and congestion control
Major performance degradation:
Frequent path breaks, presence of old routing information, high channel error rate, and frequent network partitions

8. Pricing Scheme

9. Quality of Service Provisioning
QoS often requires negotiation between the host and
the network, resource reservation schemes, priority
scheduling and call admission control
QoS in Ad hoc wireless networks can be on a per flow, per link, or per node
Qos Parameters: different applications have different requirements
– Multimedia: bandwidth and delay are the key
parameters
– Military: BW, delay, security and reliability
– Emergency search –and-rescue: availability is
the key parameters, multiple link disjoint paths
– WSN: battery life, minimum energy consumption

10. Quality of Service Provisioning
QoS-aware routing:
– To have the routing use QoS parameters for finding
a path
– The parameters are network through put, packet delivery ratio, reliability, delay, delay jitter, packet
lost rate, bit error rate, and path loss
QoS framework:
– A frame work for QoS is a complete system that
attempts to provide the promised service
– The QoS modules such as routing protocol,
signaling protocol, and resource management
should react promptly according to changes in the
network state

11. Self-Organization
An important property that an ad hoc wireless network should exhibit is organizing and maintaining the network by itself
Major activities: neighbor discovery, topology organization, and topology reorganization
Ad hoc wireless networks should be able to perform self-organization quickly and efficiently

12. Security
The attack against ad hoc wireless networks are classified into two types: passive and active attacks
Passive attack: malicious nodes to observe the nature of activities and to obtain information in the network without disrupting the operation
Active attack: disrupt the operation of the network
– Internal attack: nodes belong to the
same network
– External attack: nodes outside the network

13. Major Security Threats
Denial of service: either consume the network BW or overloading the system
Resource consumption
– Energy depletion: by directing unnecessary
traffic through nodes
– Buffer overflow: filling unwanted data, routing
table attack
(filling nonexistent destinations)
Host impersonation: A compromised node can act as
another node and respond control packets to create
wrong route entries and terminate the traffic
Information disclosure: support useful traffic pattern
Interference: create wide-spectrum noise

14. Addressing and Service Discovery
An address that is globally unique is required for a node to participate communication
– Auto-configuration of address is required
to allocate non-duplicate address to the
nodes
– In networks frequent partitioning and
merging of network components require
duplicate address detection mechanisms
Nodes in the network should be able to locate
services that other nodes provide

15. Energy Management Transmission power management:
– RF hardware design ensure minimum
power consumption
– Uses variable power MAC protocol
– Load balance in network layer
– Reducing the number of retransmissions
at the transport layer
– Application software developed for
mobile computers

16. Energy Management(cont.)
Battery energy management: extending the battery life by taking chemical properties, discharge patterns, and by the selection of a battery from a set of batteries that is available for redundancy
Processor power management: CPU can be put into different power saving modes during low processing load conditions
Devices power management: can be done by OS by selectively powering down interface devices that are not used or by putting devices into different power-saving modes

17. Scalability
The latency of path-finding involved with an on-demand routing protocol in a large ad hoc wireless network may be unacceptably high.
A hierarchical topology-based system and addressing may be more suitable for large ad hoc wireless networks

18. Deployment Considerations
The deployment of a commercial ad hoc wireless network has the following benefits
– Low cost of deployment
– Incremental deployment
– Short deployment time
– Re-configurability

19. Major Issues for Deployment
Scenario of deployment
– Military deployment
• Data-centric (e.g. WSN)
• User-centric (soldiers or vehicles carrying with wireless communication devices)
– Emergency operations deployment
– Commercial wide-area deployment
– Home network deployment
Required longevity of network: regenerative power source can be deployed when the connectivity is required for a longer duration of time
Area of coverage

20. Major Issues for Deployment
Service availability: redundant nodes can be deployed to against nodes failure
Operational integration with other infrastructure: can be considered for improve the performance or gathering additional information, or for providing better QoS
Choice of protocols: the choices of protocols at different layers of the protocol stack is to be done taking into consideration the deployment scenario